To investigate antidepressant drugs, all of which down-regulate 5HT1A receptors,in psychiatric disorders, which are responsive to these agents, in order to determine whether this is a necessary or sufficient property for manifesting a clinical response. This will be done by treating those disorders responsive to antidepressants and monitoring 5HT1A receptor down regulation in clinical responders and nonresponders to clarify the mechanism of clinical action in different disorders.